The attacks follow a mortar shelling of an Israeli outpost, which the IDF said was carried out by Islamic Jihad.
A number of mortar shells were fired from the Gaza Strip at Israeli troops, and in response Israeli tanks and aircraft targeted four Hamas positions in northern Gaza, the army said.
Following the tunnel demolition, Islamic Jihad vowed to retaliate, but Thursday's action was the first significant reaction by militants that the Israeli military ascribed to the group.
Rival Palestinian factions Fatah and Hamas agreed on Wednesday to delay the final transfer of power over the Gaza Strip from Hamas to the Western-backed Palestinian Authority government by 10 days to December 10 to allow time to "complete arrangements", officials said.
The Israeli Air Force fires at least four missiles into an area, south of Gaza city, wounding three Palestinians, who were rushed to the Shifa Medical Center, west of the city. Six militants were killed in the blast, including Islamic Jihad's field commander in Central Gaza and his senior associate, as well as two Hamas fighters.
Rival Palestinian factions jointly agreed Wednesday to ask Egypt to postpone the handover of the control over Gaza from Hamas to Fatah as part of a reconciliation agreement, they said. Later on Thursday evening, the army said it also had struck two "terror infrastructure targets".
Three people received light injures as a result of Israel's targeting of a site in the besieged Gaza Strip on 30 November 2017.
No Israelis were injured in the mortar attacks.
Israel also is building an underground barrier to prevent tunnels from crossing into Israel.